Liquid crystal display device

Abstract

A liquid crystal display device (100) includes a liquid crystal display panel (1) and an illumination element (2), and is capable of switching between: a first mode of displaying in which displaying is performed by using a plurality of color rays emitted from the illumination element; and a second mode of displaying in which the background is allowed to be perceived, with no color rays being emitted from the illumination element. Each pixel is, under the first mode of displaying, capable of switchably presenting a black displaying state with a vertical field being generated across the liquid crystal layer (30), a white displaying state with a lateral field being generated across the liquid crystal layer, or a transparent displaying state of allowing the rear face side to be visible in a see-through manner with no voltage applied to the liquid crystal layer, and, under the second mode of displaying, capable of switchably presenting a black displaying state with a vertical field being generated across the liquid crystal layer, a transparent displaying state of allowing the rear face side to be visible in a see-through manner with no voltage being applied to the liquid crystal layer, a white displaying state with essentially only a vertical field being generated across the liquid crystal layer, or an intermediate level displaying state with essentially only a vertical field being generated across the liquid crystal layer.

The invention claimed is: 
     
       1. A liquid crystal display device comprising:
 a liquid crystal display panel including a first substrate and a second substrate opposed to each other and a liquid crystal layer interposed between the first substrate and the second substrate; and 
 an illumination element provided at a rear face of the liquid crystal display panel, the illumination element being capable of switchably irradiating the liquid crystal display panel with a plurality of color rays and being light-transmissive when not radiating any color rays, 
 the liquid crystal display device having a plurality of pixels arranged in a matrix array on the liquid crystal display panel, wherein, 
 the first substrate includes a first electrode provided in each of the plurality of pixels, and a second electrode provided under the first electrode via an insulating layer, the second electrode generating a lateral field across the liquid crystal layer in cooperation with the first electrode; 
 the second substrate includes a third electrode opposed to the first electrodes and the second electrodes, the third electrode generating a vertical field across the liquid crystal layer in cooperation with the first electrode and the second electrode; 
 the liquid crystal display device is configured to be capable of switching between a first mode of displaying where multicolor displaying is performed by using the plurality of color rays emitted from the illumination element and a second mode of displaying where a background is allowed to be perceived through the illumination element with no color rays being emitted from the illumination element; 
 each of the plurality of pixels is, 
 under the first mode of displaying, capable of switchably presenting 
 a black displaying state of performing black displaying with a vertical field being generated across the liquid crystal layer, 
 a white displaying state of performing white displaying with a lateral field being generated across the liquid crystal layer, or 
 a transparent displaying state of allowing the rear face side of the liquid crystal display panel to be visible in a see-through manner with no voltage being applied across the liquid crystal layer, and, 
 under the second mode of displaying, capable of switchably presenting 
 a black displaying state of performing black displaying with a vertical field being generated across the liquid crystal layer, 
 a transparent displaying state of allowing the rear face side of the liquid crystal display panel to be visible in a see-through manner with no voltage being applied across the liquid crystal layer, 
 a white displaying state of performing white displaying with essentially only a vertical field being generated across the liquid crystal layer, or 
 an intermediate level displaying state of performing intermediate level displaying with essentially only a vertical field being generated across the liquid crystal layer. 
 
     
     
       2. The liquid crystal display device of  claim 1 , wherein, under the second mode of displaying,
 a first potential difference exists between the first electrode and the second electrode in the black displaying state, and, 
 in the intermediate level displaying state and the white displaying state, a potential difference exists between the first electrode and the second electrode which is smaller than the first potential difference. 
 
     
     
       3. The liquid crystal display device of  claim 1 , wherein,
 under the first mode of displaying, a second potential difference exists between the first electrode and the second electrode in the white displaying state, and, 
 under the second mode of displaying, a third potential difference which is smaller than the second potential difference exists in the white displaying state. 
 
     
     
       4. The liquid crystal display device of  claim 1 , wherein, under the second mode of displaying, an applied voltage to the first electrode and an applied voltage to the second electrode become lower with an increasing gray scale level from a lowest gray scale level to a gray scale level corresponding to the white displaying state. 
     
     
       5. The liquid crystal display device of  claim 4 , wherein, under the second mode of displaying, the applied voltage to the first electrode and the applied voltage to the second electrode become lower, at a constant rate, with an increasing gray scale level from the lowest gray scale level to the gray scale level corresponding to the white displaying state. 
     
     
       6. The liquid crystal display device of  claim 5 , wherein a ratio of the applied voltage to the second electrode to the applied voltage to the first electrode is kept substantially constant between the lowest gray scale level and the gray scale level corresponding to the white displaying state. 
     
     
       7. The liquid crystal display device of  claim 6 , wherein, under the second mode of displaying, the applied voltage to the first electrode and the applied voltage to the second electrode remains equal between the lowest gray scale level and the gray scale level corresponding to the white displaying state. 
     
     
       8. The liquid crystal display device of  claim 1 , further comprising an insulating layer interposed between the first electrode and the second electrode, wherein,
 the first electrode includes a line portion and a space portion; and 
 the insulating layer is exposed in a region corresponding to the space portion. 
 
     
     
       9. The liquid crystal display device of  claim 1 , wherein multicolor displaying is performed by a field sequential method under the first mode, and multicolor displaying by a field sequential method is not performed under the second mode.